Dietary exposures being assessed in human populations include consumption of specific food groups, such as meat or fruits and vegetables or the Brassica genus; and specific foods, such as beef or ethnic items; macronutrient and micronutrient intake, such as fat, vitamin A, carotene, or vitamin C; general nutritional status; metabolic indices, such as serum cholesterol or serum vitamin A; food additives; and cooking practices. Cancers being studied include those of the colon, rectum, breast, esophagus, lung, pharynx, and oral cavity, pancreas, stomach, and kidney. Case-control studies have been initiated in high-risk areas with unusually high mortality from cancers conceivably related to diet and among migrants whose changing cancer rates appear related to new lifestyles such as Japanese-Americans. Case-control studies have also been designed to test specific hypotheses generated by animal or in vitro experiments. Data from HANES I and II and the USDA Food Consumption Survey are being analyzed to test specific hypotheses, such as the relationship of age at menarche to diet, and to provide descriptive information on U.S. dietary patterns, diet variation, and nutrient intake and its determinants.